1. Field of the Invention
The present invention relates to a method of manufacturing a ceramic superconductor and, more particularly, to a method of manufacturing a compound superconductor such as an oxide superconductor with poor workability.
2. Description of the Related Art
Ceramic superconductors such as oxide superconductor having higher critical temperatures than those of alloys (e.g., NbTi, NbZr, and NbTiZr) and intermetallic compounds (e.g., Nb.sub.3 Sn, Nb.sub.3 Al, and Nb.sub.3 (AlGe)) industrially have received a great deal of attention. Typical ceramic superconductors are:
(1) La.sub.2 CuO.sub.4 superconductors such as (LaBa).sub.2 CuO.sub.4 and (LaSr).sub.2 CuO.sub.4 ;
(2) LnBa.sub.2 Cu.sub.3 O.sub.y superconductors (wherein Ln represents rare earth elements excluding Ce and Tb);
(3) Bi-Sr-Ca-Cu-O superconductors such as BiSrCaCu.sub.2 O.sub.x, Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.x (x=8), and Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x (x=10); and
(4) Tl-Ba-Ca-Cu-O superconductors such as Tl.sub.2 Ba.sub.2 CaCu.sub.2 O.sub.8 and Tl.sub.2 Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.10.
Superconductors (1) have critical temperatures Tc of 30 to 50 K. Superconductors (2), (3), and (4) have higher critical temperatures Tc, especially those equal to or higher than a liquid nitrogen temperature. These are superconductors of Type 2 and have upper critical magnetic fields as high as 10 to 200 T. They are expected to be also used for magnets of high magnetic fields.
However, these materials have poor workability. It is very difficult to form the materials into wires and strips required for wires, cables, magnet coil conductors, and the like. An attempt has been made to deposit such a material on a wire or strip substrate by a Physical Vapor Deposition method such as vapor deposition or sputtering. However, this attempt has led to only poor productivity. An effective method has not yet been proposed so far.
Strong demand, therefore, has arisen for developing a technique for satisfying the following points in view of the background described above:
(1) To provide a method of manufacturing wires and strips prepared by effectively utilizing characteristics (Tc, Hcl, Hc2, etc.) inherent to ceramic superconductors;
(2) To provide a method of working a mechanically weak ceramic body into a long wire or strip having a desired shape;
(3) To obtain a superconductor through which a superconducting current flows to as high a critical current density (Jc) as possible;
(4) To stabilize the superconducting current in practice without causing a quenching phenomenon;
(5) To obtain a superconductor having practical mechanical strength and durability against deformation and strain;
(6) To obtain a superconductor which is not denatured by a reaction with moisture, gases and chemicals in outer atmosphere during fabrication, storage, and the service life of the superconductor built into equipment and to assure a long service life; and
(7) To achieve the above purposes on industrial and economical basis.